@stdlib/math-base-special-croundn

roundn

Round a complex number to the nearest multiple of 10^n.

Installation

npm install @stdlib/math-base-special-croundn

Usage

var croundn = require( '@stdlib/math-base-special-croundn' );

croundn( [out,] re, im, n )

Rounds a complex number comprised of a real component re and an imaginary component im to the nearest multiple of 10^n.

// Round components to 2 decimal places:
var v = croundn( -3.141592653589793, 3.141592653589793, -2 );
// returns [ -3.14, 3.14 ]

// If n = 0, `croundn` behaves like `cround`:
v = croundn( -3.141592653589793, 3.141592653589793, 0 );
// returns [ -3.0, 3.0 ]

// Round components to the nearest thousand:
v = croundn( -12368.0, 12368.0, 3 );
// returns [ -12000.0, 12000.0 ]

v = croundn( NaN, NaN, 0 );
// returns [ NaN, NaN ]

By default, the function returns real and imaginary components as a two-element array. To avoid unnecessary memory allocation, the function supports providing an output (destination) object.

var Float32Array = require( '@stdlib/array-float32' );

var out = new Float32Array( 2 );

var v = croundn( out, -4.6, 5.5, 0 );
// returns <Float32Array>[ -5.0, 6.0 ]

var bool = ( v === out );
// returns true

Notes

• When operating on floating-point numbers in bases other than 2, rounding to specified digits can be inexact. For example,

  var x = 0.2 + 0.1;
  // returns 0.30000000000000004
  
  // Should round components to 0.3:
  var v = croundn( x, x, -16 );
  // returns [ 0.3000000000000001, 0.3000000000000001 ]

Examples

var Complex128 = require( '@stdlib/complex-float64' );
var randu = require( '@stdlib/random-base-randu' );
var ceil = require( '@stdlib/math-base-special-ceil' );
var real = require( '@stdlib/complex-real' );
var imag = require( '@stdlib/complex-imag' );
var croundn = require( '@stdlib/math-base-special-croundn' );

var re;
var im;
var z;
var o;
var w;
var n;
var i;

for ( i = 0; i < 100; i++ ) {
    re = ( randu()*100.0 ) - 50.0;
    im = ( randu()*100.0 ) - 50.0;
    z = new Complex128( re, im );

    n = ceil( randu()*5.0 );
    o = croundn( real(z), imag(z), -n );
    w = new Complex128( o[ 0 ], o[ 1 ] );

    console.log( 'roundn(%s,%s) = %s', z.toString(), n.toString(), w.toString() );
}

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See Also

• @stdlib/math/base/special/cceiln: round a complex number to the nearest multiple of 10^n toward positive infinity.
• @stdlib/math/base/special/cfloorn: round a complex number to the nearest multiple of 10^n toward negative infinity.
• @stdlib/math/base/special/cround: round a complex number to the nearest integer.

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Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2022. The Stdlib Authors.